Sheet-metal tube



(No Model.)

P. A. WILMOT. SHEET METALTUBE.

N0. 578,799. Patented Mar. 16, 1897.

WITNESSES I VENT R 75MQ% M%%M PATENT OFFICE.

FRANK A. VVILMOT, OF ISRIDGEPORT, CONNECTICUT.

SHEET-METAL TUBE.

SPECIFICATION forming part of Letters Patent No. 578,799, dated March16, 1897.

Application filed March 13, 1896. Serial No. 583,061. (No model.)

To all whom it may concern.-

Be it known that LFRANK A.VVILMOT, a citizen of the United States,residing at Bridgeport, in the county of Fairfield and State ofConnecticut, have invented certain new and useful Improvements inSheet-Metal Tubes; and I do hereby declare the following to bea full,clear, and eXact description of the invention, such as will enableothers skilled in the art to which it appertains to make and use thesame.

My invention relates to the class of metal tubes which are formed bycurving a blank of sheet metal the meeting edges of which are providedwith interlocking projections and recesses; and the object of myinvention is to produce a tube of this character which may be made, ifrequired, of clock-spring metal, is so constructed that the cost ofproduction shall be reduced to the minimum, the projections anddepressions being so shaped as to produce the least possible wear uponthe dies and punches, and in which the projections and depressions willinterlock readily and when once interlocked and the final compressionhas been given to the tube will not unlock under any circumstanceswhatever, the tube being equally as strong at the joint as at anyportion.

With these ends in View I have devised the novel tube of which thefollowing description, in connection with the accompanying drawings, isa specification, letters and numbers being used to designate the severalparts.

Figure 1 is aview illustrating the completed tube, the projections anddepressions having been interlocked and clenched; and Fig. 2 is a viewshowing the edges of the blank curved toward each other and in positionto be interlocked.

It is of course well understood that in making this class of tubes theblanks are made of slightly-greater width than is necessary to encirclethe mandrel, that in all diework, especially in cutting steel, it isdesirable that the lines of the punches be right lines, and,furthermore, that it is desirable that the projections and recessesshall be so shaped that the projections will pass directly intotherecesses without the necessity of placing the projections over therecesses and then forcing them down into the recesses.

The objection heretofore found in making tubes from blanks the edges ofwhich were provided with straight-sided projections which were forcedinto straight-sided recesses has been that the resiliency of the metalfrequently causes the edges of the blank to separate more or less at thejoint. This is especially true when metal of the character known asclock-spring steel is used, this grade of metal being especially adaptedfor use in the manufacture of bicycleframes, where great strength andstiffness is required with the least possible weight, it beingimpossible, moreover, to formfroni the edges of a tubeblank made fromthis metal the usual lockjoiut, as the metal will break when bent at asharp angle. In my novel tubes the usual lock-joint is dispensed with,and I wholly overcome the objection of separation at the joint by soshaping the projections and recesses that when the final compression isgiven to the blank about the mandrel the projections will be clenched inthe recesses in such a manner as to leave a perfect1y-tight joint, ifrequired, and under allcircumstances to prevent the edges of the blankfrom separating. This feature is especially valuable when the tubes areused in the manufacture of bicycle-frames, as it enables me to use lightstiif metal and to lock the edges of the blank by means ofstraight-sided interlocking projections and recesses. This I have foundto be impracticable without my novel improvement for the reason that theheat necessarily applied in brazing the tubes to the connections isliable to melt the solder in the joints, and then the resiliency of themetal opens the joints.

A denotes a blank the edges of which are provided with alternateprojections a and depressions b. The novel feature of my invention isthat I provide at the base of a portion or all of these depressions lugs1, which engage the walls 2 at the ends of the correspondingprojections. The walls are provided with angular recesses, as shown inthe drawings, leaving points 3 at the edges of the projections. When theedges of the blank are closed together, the projections are forced intothe corresponding recesses, and when the final compression is given tothe blank about the mandrel the lugs 1 will engage the walls 2 at theends of the projections and will force the side Walls of theprojectionsoutward, causing them to engage the side Walls of thedepressions, thereby firnrly clenching and locking the projections inthe depressions, so that the tube is made as strong at the joint as atany other place.

In Fig. 2 I have shown the sides of the recesses in Walls 2 as lying atmore acute angles to the line of the joint than the sides of lugs 1, andhave also shown the tips of lugs I 1 as flattened, as at 4. The effectof this special construction is to spreadthe points 3 in oppositedirections and interlock them and also to leave slight openings entirelythrough the completed tube, as indicated at 5 in Fig.

1. The purpose in leaving these openings is claim- 1. A tube formed froma blank of sheet metal having upon its edges. a continuous series ofinterlocking projections and depressions, said depressions havingangular lugs at their bases and said projections having angular recessesat their ends leaving points 3 at the'edges thereof, so that when thefinal compression is given to the blank said lugs will engage therecesses in the corresponding projections and Will force the side Wallsof the projections outward into engagement With the side walls of thecorresponding depressions, thereby clenching the edges of the blank inthe interlocked positions.

2. A tube formed from a blank of sheet metal-havin g upon its edgesinterlocking proj cations and depressions, said depressions beingprovided at their bases with lugs having flattened tips and the frontWalls of the corresponding projections being recessed as shown so thatWhen the final compression is given to the blank the lugs will force theside Walls of the projections outward into engagement With the sideWalls of the depressions and the edges of the blank Will be clenched inthe interlocked position leaving openings through the joint between thetips of the lugs and the bases of the recesses as and for the purposeset forth.

In testimony whereof I affix my signature in presence of two Witnesses.

FRANK A. \VILMO'I.

\Vitnesses:

A. M. WoosTER, S. V. RICHARDSON.

